This invention relates to novel photopolymerizable compositions having high photospeed. Still more particularly, it relates to compositions having novel combinations of chemical compounds as initiators for photopolymerization.
It is known to add certain light absorbing compounds to photopolymerizable compositions containing ethylenically unsaturated monomers for the purpose of increasing the photographic sensitivity of the compositions. The use of .alpha.-dicarbonyl compounds and combinations of .alpha.-dicarbonyl compounds with ultraviolet radiation-absorbing ketones for photoinsolubilization of photocrosslinkable polymers has been disclosed, e.g., in Laridon, et al., U.S. Pat. No. 3,427,161. However, cyclic cis-.alpha.-dicarbonyl compounds are not generally known as photoinitiators in the prior art and have been shown to initiate photopolymerization very poorly (viz., Notley, U.S. Pat. No. 2,951,758, Col. 5, line 39). Surprisingly, it has been found that certain radiation absorbing compounds can transfer energy to the cis-.alpha.-dicarbonyl compounds and act as sensitizers therefor. Photopolymerizable compositions containing the novel cis-.alpha.-dicarbonyl-sensitizer combinations of this invention have been demonstrated to have greatly improved photospeed and may be chosen to provide a wide range of spectral sensitivity.